docs: add apollo rust client

[liushv0]

What's the purpose of this PR

add comment of rust adk for apollo

Which issue(s) this PR fixes:

Fixes #None

Brief changelog

docs: add apollo rust client

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[nisiyong]

Nice works! Thanks @liushv0 for contributing to the Rust language client.

And I think maybe we should use gRPC to replace the client protocol HTTP in the future to support multi-language, what do you think? @nobodyiam

[nobodyiam]

@nisiyong We may add the grpc support in the future but should still keep the HTTP/1.1 protocol for a while to make it backward compatible.

[nobodyiam]

LGTM

[nisiyong]

@nisiyong We may add the grpc support in the future but should still keep the HTTP/1.1 protocol for a while to make it backward compatible.

It makes sense, we could do it in 2023.